Conventionally, a nuclear reactor vessel is housed in a nuclear reactor building in a state in which the nuclear reactor vessel is supported by a structure of a nuclear reactor building (for example, see Patent Literature 1).
For example, a member (a support) affixed to the structure is mounted in a nuclear reactor vessel and the support is affixed to the structure so as to be supported by the structure.
In addition, the support needs to be securely affixed to the structure and integrally formed with the structure so that the support is not deformed due to a vertical load or a horizontal load during an earthquake. Therefore, the support is affixed to the structure by welding when affixing to the structure.